Explosives liner

ABSTRACT

Described herein is a method of filling ordnance with explosive materials. An ordnance shell ( 2 ) comprises a cavity ( 32 ) filled with explosive material ( 10 ), the explosive material ( 10 ) being contained in a bag ( 36 ) located within the cavity ( 32 ).

This invention relates to the field of the filling of ordnance withexplosive materials.

Traditional methods used for filling ordnance with polymer bondedexplosive (PBX) utilise a filling process based on the combination ofusually two materials (an explosive mixture (pre-mix) and a hardener).The two materials are mixed together and injected into the volumereserved for explosive materials usually at the tip of the ordnance.

In a typical application of the mixing and filling process, a pre-mix ofexplosive is produced and typically mixed with a hardener (i.e. IPDI)the mixture mixed together to produce a combined final explosivematerial (e.g. PBX).

Ordnance to be filled is typically placed in a vacuum chamber and afilling attachment from the bottom outlet valve of the mixer bowlcontaining the fully mixed PBX composition is attached to the chamber.Typically, the vacuum chamber will be evacuated to <100 millibars.

The vacuum provides the physical motivation for the fully combined finalexplosive material to flow into the ordnance. However, the interactionof the combined final explosive material and the inner surface of thevolume to be filled can lead to problems in terms of the inadvertentadhesion of the material to the sides of the volume during filling. Thisintroduces the possibility of an imperfect fill of the explosive cavity.An imperfect fill of explosives may result in ordnance failing safetyacceptance tests, the ordnance being liable to early detonation due tothe movement of explosive material within the ordnance as it islaunched.

In addition to the problems associated with the issue of imperfect fill,ordnance can be subject to environmental cycling, including temperaturecycling, which can cause the explosive material contained within theordnance to lose some of its required physical characteristics.

The problems associated with imperfect fill and environmental cyclingare known in the art and attempts to solve these problems have been madeby the use of approaches, such as liners which are sprayed or pouredonto the inner surface of the explosives cavity or volume within theordnance. This liner would in turn adhere to the wall of the explosivesvolume in an attempt to reduce the effects of explosive adhesion andenvironmental cycling.

However, the problems associated with the state of the art solutionsrelate to the fact that the liner does indeed adhere to the wall of theexplosives volume, and consequently the explosive filling therebysuffers from some of the effects induced by environmental/temperaturecycling and physical vibration that would have also been observed had noliner been present.

Additionally, when ordnance is required to be disposed of at the end ofits service life explosive materials comprising PBX cannot beeffectively ‘boiled out’ as in the case of TNT based explosives, and anexpensive decommissioning process has to be put in place requiring theeffective cutting in two or more parts of the ordnance, to allow for theextraction of the PBX explosives which will have adhered to the innerwall of the explosive volume.

The invention described herein provides for apparatus and a method forreducing the problems associated with the filling of explosives,especially in the case of explosives comprising PBX materials and thelike, and for drastically reducing the effects of environmental andtemperature cycling on the physical quality of the explosive filling.

Additionally the invention described herein provides for an improvedmethod of decommissioning ordnance containing PBX based explosives andthe like.

Accordingly there is provided ordnance comprising a cavity filled withexplosive material, said explosive material being contained in a bagwithin said cavity.

In a first preferred embodiment of the invention the bag is made of anelastomeric material.

Preferably said elastomeric bag will have a volume less that that of theexplosives cavity of said ordnance.

In a further preferred embodiment of the invention the elastomeric bagwill have a volume in the range 5% to 10% less than that of theexplosives cavity of said ordnance.

Additionally there is provided a method of filling ordnance withexplosive materials, comprising the use of a bag in accordance withanother aspect of the invention, said bag being inserted into theexplosives cavity of said ordnance, said bag then being filled withexplosive materials.

In a further preferred embodiment of the invention a bag in accordancewith the invention is forced against the walls of said explosives volumeby the action of a vacuum source.

The invention is now described by way of example only with reference tothe following drawing, in which FIG. 1 is a diagrammatic representationof an explosives filling bag and ordnance filling apparatus inaccordance with the invention.

FIG. 1 shows a top section of an ordnance shell 2 being filled withexplosive material 10, the ordnance having both an outer surface 4 andan inner surface 6, the inner surface describing a cavity 32 for housingexplosive material 10.

Explosive material 10 enters the cavity 32 via a filling tube 30, theflow of the explosive material into the cavity 32 being controlled by avalve 28.

A vacuum filling attachment 12 is secured over the aperture 34describing the opening in the cavity 32 such that a substantiallyairtight seal is produced between the atmosphere and the volume withinthe cavity 32. Vacuum means 14 is provided, the vacuum means 14 beingconnected to the filling attachment 12 such that any gas such as airwithin the cavity 32 can be partially or wholly evacuated by the actionof the vacuum port 18 thereby providing a motivating force for explosivematerial to flow through the valve 28 when opened, down the filling tube30 and into the cavity 32.

Additional vacuum ports 16 and 20 are also shown, the vacuum line shownat 22 shown stopped for illustrative purposes only but actuallyreturning to the vacuum source 14.

An elastomeric bag 36 is shown held within the cavity 32 of the ordnanceshell 2 by the vacuum filling attachment 12. The main vacuum ports 16and 20 have corresponding smaller ports to enable a vacuum to be createdwithin the space 8 defined by the bag 36 and the inner wall 6 of thecavity 32. The action of this vacuum in extracting gas such as air fromwithin the cavity 8 provides the force required to hold the bag 36against the inner wall 6 of the cavity 32 thereby providing a bag linedcavity 32 into which the explosive material 10 can be injected.

The elastomeric bag 36 is between 5% and 10% smaller than the shellcavity 32 to ensure that the explosive material (filling) 10 does notadhere to the inner wall 6 of the ordnance shell 2. The bag 36 alsoensures that the filling 10 survives environmental changes withoutcracking. The bag 36 provides a barrier between the filling 10 and theordnance shell 2 which stretches and shrinks with the filling 10.

In order to maintain contact between the bag 36 and the inner wall 6 inthe presence of the vacuum force generated within the cavity 32 by thevacuum port 18, there must be a differential in the two vacuums producedin favour of the bag vacuum.

The diagram shows a non-contact level sensor 40 present within thecavity 32, the sensor 40 providing a method of sensing the fill volumeof the explosive 10 within the cavity 32. The output from the sensor 40can be fed back to a control means for effecting the action of the valve28 and indeed aspects of the explosives process not shown. The sensor 40therefore controls the filling height of the explosive material as anon-contact fill-to-level device.

The non-contact level sensor 40 may comprise an optical sensor, a fibreoptic sensor, a laser or an LED.

The decommissioning of ordnance comprising a bag in accordance with theinvention is simplified over the now prior art. The bag can bemanufactured with an anti-adhesion surface to prevent adhesion betweenthe bag and the inner lining of the cavity. Alternatively, the cavitylining itself can be treated with an anti-adhesion material prior tointroducing the bag. When subsequently decommissioning the ordnance, thebag containing the explosives can be removed as a whole (if the ordnancedesign allows) thereby reducing the exposure of the persondecommissioning the ordnance to the explosive material. Where theordnance design does not allow removal of the bag containing theexplosives as a whole (e.g. in the case of artillery shell) then asingle transverse cut across the major internal diameter of the ordnanceshould allow the bag containing the explosives to be easily removed intwo parts.

The other advantages of the invention will be readily apparent to thoseskilled in the art and the substitution of elements for mechanicalequivalents and adaptation of the process using different materials andthe like should be construed as being comprised within the inventiveconcept as claimed.

References to ordnance in the above specification and claims shall beconstrued as non-limiting and in respect of the invention shall includewithout limitation shells, mortars, rockets, bombs, warheads,projectiles and any other weapons or containers which are required to befilled with a combined explosive mixture.

1. Ordnance comprising a cavity filled with explosive materials, saidexplosives material being contained in a bag within said cavity. 2.Ordnance in accordance with the invention described in claim 1 whereinthe bag is made of an elastomeric material.
 3. Ordnance in accordancewith the invention described in claim 1 wherein said bag has a volumeless than that of the explosives cavity of said ordnance.
 4. Ordnance inaccordance with the invention described in claim 1, wherein the bag willhas a volume in the range 5% to 10% less than that of the explosivescavity of said ordnance.
 5. A method of filling ordnance with explosivematerials, comprising the use of a bag in accordance with claim 1wherein, said bag is inserted into the explosives cavity and filled withexplosive materials.
 6. A method of filling ordnance with explosivematerials in accordance with claim 5, wherein the bag is forced againstthe inner walls of the explosives cavity by the action of a vacuum.
 7. Amethod of filling ordnance with explosive materials in accordance withclaim 5 wherein a differential vacuum is produced between the bag andinner cavity wall and the main explosives cavity.
 8. A method of fillingordnance with explosive materials in accordance with claim 5, furthercomprising the use of fill-to-level control means utilizing at least onefiber optic sensor. 9-10. (canceled)